The present invention relates generally to video recorders, and in particular to a video tape recording and reproducing apparatus having an edit mode for inserting a new program into prerecorded material without causing disturbances during transitions at the boundaries between different programs.
In conventional video tape recorders of the helical scan type having a pair of rotary heads with which the video signal is recorded along skewed parallel tracks, a stationary head is employed for recording a tracking signal along an edge of the videotape in synchronism with the picture field of the video signal so that the recorded tracking signal corresponds in position to each oblique track. During playback modes the tracking signal is detected to generate a reference phase with which the speed of revolution of the rotary heads is compared to detect a difference between them. The transport speed of the tape is controlled in response to the detected phase difference so that the video heads are precisely kept on track. The recent tendency in video recording is toward increasing the amount of information recorded on a tape, whereby tracks are closely spaced apart and tape transport speed is decreased. It is, however, difficult to ensure continuity in the tracking signal when new material is superimposed or "inserted" into a prerecorded program by operating the apparatus in a playback mode. On reproduction of such videotapes the tracking signal is lost at the boundary between the different programs and the picture is completely disturbed.
On the other hand, a video recorder which has recently been developed employs a pilot signal which is recorded through the rotary heads on each track with the video signal to identify the track. However, the video recorder of this type still suffers from the above-mentioned difficulty.